.\"     $NetBSD: sa_yield.2,v 1.4 2004/05/09 11:28:58 yamt Exp $
.\"
.\" Copyright (c)2004 YAMAMOTO Takashi,
.\" All rights reserved.
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.\" ------------------------------------------------------------
.Dd May 9, 2004
.Dt SA_YIELD 2
.Os
.Sh NAME
.Nm sa_yield
.Nd idle a virtual processor
.\" ------------------------------------------------------------
.Sh LIBRARY
.Lb libc
.\" ------------------------------------------------------------
.Sh SYNOPSIS
.In sa.h
.Ft int
.Fn sa_yield
.\" ------------------------------------------------------------
.Sh DESCRIPTION
.Fn sa_yield
is used to idle a virtual processor on which the calling thread is running.
It's typically used when the process's userland scheduler has no userland
thread to run.
.Pp
Scheduler activation should be enabled by
.Fn sa_enable
beforehand.
.\" ------------------------------------------------------------
.Sh RETURN VALUES
On success,
.Fn sa_yield
will not return to userland in the normal way.
It returns into an upcall hander with an upcall.
Otherwise, a value of \-1 is returned and
.Va errno
is set to indicate the error.
.\" ------------------------------------------------------------
.Sh SEE ALSO
.Xr sa_enable 2 ,
.Xr pthread 3
